* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
#app {
  height: 100vh;
  display: flex;
  flex-direction: column;
}
#app .topNav {
  display: flex;
  align-items: center;
  padding: 0 10px;
  height: 40px;
}
#app .topNav .title {
  text-align: center;
  flex: 1;
}
#app .mainContent {
  background-color: #eee;
  flex: 1;
  display: flex;
}
#app .mainContent .left {
  background-color: rosybrown;
  width: 80px;
}
#app .mainContent .left .item {
  padding: 5px 10px;
}
#app .mainContent .right {
  background-color: goldenrod;
  flex: 1;
}
#app .mainContent .right .item {
  padding: 10px;
}
